docs: def migrate(self, mapping, index, doc_type):
          """
          Migrate a ES mapping
  
  
          :param mapping: new mapping
          :param index: index of old mapping
          :param doc_type: type of old mapping
          :return: The diff mapping
          """
          old_mapping = self.get_doctype(index, doc_type)
          #case missing
          if not old_mapping:
              self.connection.indices.put_mapping(doc_type=doc_type, mapping=mapping, indices=index)
              return mapping
              # we need to calculate the diff
          mapping_diff = old_mapping.get_diff(mapping)
          if not mapping_diff:
              return None
          from pprint import pprint
  
          pprint(mapping_diff.as_dict())
          mapping_diff.connection = old_mapping.connection
          mapping_diff.save()